Hi Jim,
Working in the auto industry all those years, we always called this thing the Instrument Panel, because that's where the instruments were housed. But, for some reason it's called the Dash on the GT40, and so I bow to that. Anyway, enough for an automotive history lesson and back to your question. Are you talking about the fitment of the Dash itself, or the placement of the Instruments & switches in it? The fitment, of course depends on which roll bar/cage you have. Instrument placement would depend on how original you want it to look. Lots of build pics and help with all of that on this forum. Ask and you shall receive...
Rod